Explosion-proof pilot light



Nov. 14, 1950 w. c. PEARsoN 2,529,706

I EXPLOSION-PROOF PILOT LIGHT Filed Jan. 13, 1949 lll l f7 32g. Z

In FE. 27 fr' h//a//w @Mayo/V Patented Nov. 14, 1950 UNITED 2,529,7 06 EXPLOSION -PROOF PILOT LIGHT William C. Pearson, Chicago, Ill., assigner to The Pyle-National Company, Chicago, Ill., a corporation of New Jersey Application January 13, 1949, Serial No. 70,631

3 Claims. 1

This invention relates generally to an illumination apparatus and more particularly to an explosion-proof lighting xture which may be adapted to serve as an indicator means wherever electric control circuits are used.

In many industries today hazardous explosive concentrations of gaseous vapors or dust-laden air surround and permeate various pieces of machinery used in carrying out operations. These industries include the flour milling trade, the mining industries and particularly, that part of the petroleum industry having large mechanical installations in the form of cracking plants and distilleries. Wherever it is necessary to use a piece oi machinery in a hazardous environment such as a gasoline pump, or for example, an ammunition elevator aboard a warship, it is highly desirable that a suitable indicator light, or pilot light, be provided for the purpose of indicating the status of the electric control circuit associated therewith. The pilot light, too, must be explosion-prooi if property and personnel are to be adequately safeguarded.

It is further desirable in some industries to employ an explosion-proof pilot light xture assembly which embodies a plurality of jewel indicater lights, each jewel being arranged to reiiect a color of dierent hue, as may be necessary, for example, to indicate various levels in tanks containing highly volatile liquids.

A great number of so-called explosion-proof pilot lights have been provided heretofore and as a result the manufacturers and producers of explosion-prooi pilot light xtures have attempted to guide the lines of their developments in accordance with a rigid set of standards prescribed the Underv-Jriters Laboratories.

Qne particular standard oi note prescribed by the Underwriters Laboratories requires thatl a shell receptacle which supports an indicator bulb must be used only in a control circuit carrying an electric load corresponding to the specific and predetermined electrical capacity of the shell receptacle. Accordingly, it is well known in the trade that explosion-proof pilot lights must be equipped with a so-called Candelabra shell receptacle for use in any installation having a maximum. service voltage of 125 volts and with an intermediate shell receptacle in any installation having a service voltage in the range from 115 volts to 25E) volts maximum.

It is sometimes desirable that a single explosion-prooi pilot fixture to be adaptable ior use on control circuits of Varying capacities. Rather than provide a number of somewhat expensive explosion-proof light fixtures, it has been deemed desirable to provide for the interchangeability of certain iixture ttings within a unit xture.

'Io that end, explosion-proof pilot lights heretofore provided have included interchangeable shell receptacles. However, the interchanging of a shell receptacle, because of the small size of the various parts, is an exacting task and requires an assembly of small iittings which can be properly expedited only in the factory.

Another undesirable characteristic of explosion-proof pilot lights heretofore provided has been the necessity of re-sealing various elements of the xture with a liquid sealing wax in order to render the xture explosion prooi. Inasmuch as this operation can only be performed by trained personnel, field replacement of shell receptacles to meet voltage loads is discouraged and dangerous laxity on the part of operating personnel is likely to ensue.

It is, therefore, an object of this invention to provide an explosion-proof pilot light iixture which overcomes the disadvantages of iixtures heretofore provided.

It is a particular object of this invention to provide a novel and improved replaceable socket unit which includes a moulded body made of non-conducting material having a shell receptacle of predetermined electrical capacity and a button-type terminal integrally moulded therein attached to a suitable pair of electrical conductors whereby replacement of a shell receptacle may be expedited by simply substituting a new socket unit.

It is a further object of this invention to provide an explosion-proof pilot light adapted to receive standardized replaceable socket units containing elements having varying electrical capacities so as to afford a particularly facile method of interchangeability.

Another object of this invention is to provide an explosion-proof lighting fixture which requires a minimum amount of machining and a minimum number of precision iittings.

It is a further object of this invention to provide an explosion-proof pilot lighting fixture having a greatly reduced number of elements therein.

Another object of this invention is to provide an explosion-proof pilot light fixture adapted to receive replaceable socket units which may be equipped with either candelabra or intermediate type shell receptacles integrally moulded therein.

A further object of this invention is to provide an explosion-proof xture which may be readily adapted to provide a plurality of indicator jewels.

A further object of this invention is to provide an explosion-proof pilot light of simplified construction having greatly improved serviceability characteristics and which is economical to manufacture.

Other objects and advantages of this invention will become manifest to those versed in the art through reference to the following detailed description and accompanying drawings in which:

Figure 1 is a plan view of an explosion-proof pilot light fixture embodying the principles of my invention;

Figure 2 is a cross-sectional view taken on line II-l of Figure l; and

Figure 3 is a bottom end view of the replaceable socket unit included in the present pilot light assembly.

As shown on the drawing:

Referring to Figures 1 and 2 an explosionproof fixture shown generally at Ill includes a body II and a cover I2.

The body I I may be provided with boss extensions as indicated at Ila which may define suitable internally threaded bores for receiving electrical conduits (not shown) in explosion-proof assembly therewith. The top of the body II denes a at surface I Ib which may be smoothly machined. It will be noted from the drawing that the body Il defines a substantially rectanl gular cavity as at IIc.

The cover member I2 is provided with a correspondingly machined flat surface I2b so as to permit snug assembly of the cover with the body II when a plurality of cap screws i3 passing through the cover and the body are drawn up tightly.

As shown on Figure 1, the pilot light fixture IE! may be mounted upon a wall bracket M by means of suitable fasteners which pass through extensions provided on the cover member I2.

As may most clearly be seen on Figure 2, the cover I2 is provided on its upper side with a pair of internally threaded counterbores as at Ia. The counterbores I2a terminate in a pair of smooth shoulders I2C which are adapted to receive a pair of jewels or colored globes I5 made of glass or plastic. The globes I5 are held in iii-m assembly with the cover I2 by means of a pair of guard members I5 which are provided with annular externally threaded portions adapted to be threadedly engaged within the counterbores I2a. Suitable cushion rings IIa made of a soft metal such as aluminum may be interposed between the guard members I6 and the annular shoulders of the globe I5 to insure -a tight sealing iit between the globes I5 and the cover I2.

It will, of course, be understood that the instant pilot light fixture is not intended to be limited to the double pilot light form herein shown inasmuch as the identical structural features of the instant fixture could be incorporated in a single pilot light or in a, pilot light fixture incorporating a large number of indicator jewels.

Referring further to Figure 2, the cover I2 is shown as being provided with a pair of internally threaded bores as at I2d. Threadedly seated within the bores I2d are a pair of replaceable socket units indicated generally by the reference t numeral II.

As may be seen on Figures 2 and 3, each of the socket units I l comprises a molded body made of non-conducting material and includes an upper cylindrical portion I'Ia which may be able for turning the socket unit I'I into the cover I2.

The socket unit I'I comprises an integral article of manufacture and preferably may be fabricated in such a manner as to include either a candela-bra type or an intermediate type shell receptacle indicated generally by reference numeral I8. Inasmuch as the Candelabra type shell receptacle is adapted for use with service voltages less than 125 volts and the intermediate type shell receptacle is adapted for use with service voltages over 115 and up to 250 volts, it will be evident that the complete socket unit assembly Il may be adapted for use in electrical installations of varying capacities.

A button-type terminal I9 carried on a suitable disk member may be integrally molded in the body of the socket assembly in proximity to the shell receptacle I8. A pair of conductor wires 2D and 2I are connected to the button-type terminal I9 and the shell receptacle I8, respectively, and are integrally molded Within the shank portion IIc of the socket unit I'I so as to extend therethrough for electrical connection to the wire leads of a control circuit. The curvilinear path described by the conductor wires 2U, 2| through the shank portion Ilc of the socket unit Il is desirable since it permits the point of egress of the conductors from the socket body to lie in symmetry relative to the configuration of the shank. This arrangement greatly facilitates molding procedures and enhances the appearance of the socket unit.

It may be noted that the dimension of the shank portion I'Ic parallel to the axis of the conductor wires must be within the limits prescribed by the Underwriters Laboratories so as to render the path traversed by the conductor Wires through the shank explosion-proof.

It will be noted that the annulal` flange I lb on the socket unit II is provided with a pair of recessed indentations as at I'Id. These recessed indentations I'Id are arranged in such a manner as to come in alignment with a pair of drilled and tapped bores formed in the cover I2 to receive a pair of locking screws 22 whereby the socket unit I 'I may be locked in place in the cover I2.

It will be apparent that when the pilot fixture I0 is completely assembled, the socket unit Il will effectively divide the assembly formed by the body II and the cover I2 into a plurality of explosion-proof compartments. Each of the socket units Il may be provided with a suitable bulb 23 which may thus be isolated in explosion-proof relationship to the body cavity I Ic in which are located the conductors 20 and 2 I.

It should be further evident that should it be desirable to change the electrical capacity of the pilot light fixture I0, as for example, if the pilot light fixture I0 is to be used in connection with a control circuit of varying service voltage, the fixture may be quickly disassembled and an alternate socket unit II may be replaced as an integral unit thereby accomplishing eifective interchangeability without destroying the explosion-proof eii'icacy of the fixture. Because of the simplicity of the various elements contained in the instant pilot light fixture, this procedure may be followed without resorting to the use of special tools or without necessitating the attention of a skilled mechanic.

It will be apparent to those skilled in the art that I have described a novel and improved explosion-proof pilot light xture which has a greatly reduced number of elements of simplified design and which may be effectively serviced by relatively inexperienced personnel. It will be further apparent that various details of the present invention may be subjected to modication without departing from the spirit thereof. Therefore, it should be understood that the embodiment herein disclosed is not to be considered as a limitation inasmuch as I desire to be limited only by the scope of the appended claims and the prior art.

I claim as my invention:

1. An explosion-proof pilot light fixture comprising a substantially rectangular shell-like body portion dening a pair of concentric internally threaded bores in an upper part thereof, a socket unit comprising a molded plastic body having a receptacle shell and conductor wires integrally molded therein, said socket unit body dening an externally threaded cylindrical portion for removable assembly in one of said bores of said body and a light transmitting enclosure unit removably received in the other of said bores of said body.

2. An explosion-proof pilot light fixture comprising a body member, a cover carried by said 'body in snug assembly therewith, said cover dening a first internally threaded bore on the lower side thereof for receiving a removable socket unit therein, said cover dening a second internally threaded bore on the upper side thereof for receiving a light transmitting enclosure unit therein, a socket unit comprising a molded plastic body having a receptacle shell and conductor wires integrally molded therein, said socket unit body deiining an externally threaded cylindrical portion for removable assembly in said rst bore and said light transmitting enclosure unit receivable in said second bore.

3. In explosion-proof illumination apparatus of the type used for indicator purposes and generally characterized as a pilot light xture, the improvement comprising a fixture body defining an internally threaded bore, a removable socket unit, said socket unit including a substantially cylindrical body portion externally threaded for engagement with the fixture body, said externally threaded body portion together with the fixture body dening a ilame-proof joint when in assembled relationship, a shell receptacle to receive a bulb of predetermined electrical capacity and electrical conductors connected to said receptacle, said receptacle and said conductors being integrally molded in said socket unit, the length of the socket unit parallel to the conductor wires being of such dimension as to render the path traversed by the conductor wires llame-proof, whereby said pilot light fixture may be quickly adapted for varying electrical capacities by replacement of a complete socket unit.

WILLIAM C. PEARSON.

REFERENCES CITED The following references are of record in the iile of this patent:

UNITED STATES PATENTS Number Name Date 441,059 Collier NOV. 18, 1890 1,664,228 Sparkes Mar. 27, 1928 1,858,819 Corbett May 17, 1932 FOREIGN PATENTS Number Country Date 365,785 Italy Dec. 13, 1938 

